1. Field of the Invention
The present invention relates to a wireless communication system for performing communication mutually among a plurality of wireless stations as in a wireless LAN (Local Area Network), a wireless communication apparatus for use therewith, a wireless communication method for use therewith, and a computer program for use therewith, and in particular relates to a wireless communication system in which each communication station performs network operations in an autonomously distributed manner without having a relationship between a control station and a controlled station, a wireless communication apparatus for use therewith, a wireless communication method for use therewith, and a computer program for use therewith.
More particularly, the present invention relates to a wireless communication system for performing multi-hop transmission from a communication station of a transmission source to a communication station of a transmission destination via one or more relay stations in a communication environment in which each communication station performs network operations in an autonomously distributed manner, a wireless communication apparatus for use therewith, a wireless communication method for use therewith, and a computer program for use therewith, and in particular relates to a wireless communication system for performing multi-hop transmission in accordance with a routing creation protocol in which the improvement in the frequency usage efficiency is set as metrics in a communication environment in which each communication station performs communication operations in an autonomously distributed manner, a wireless communication apparatus for use therewith, a wireless communication method for use therewith, and a computer program for use therewith.
2. Description of the Related Art
Examples of standard specifications relating to a wireless network include IEEE (The Institute of Electrical and Electronics Engineers) 802.11 (for example, refer to International Standard ISO/IEC 8802-11: 1999 (E) ANSI/IEEE Std 802.11, 1999 Edition, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications), Hiper LAN/2 (for example, refer to ETSI Standard ETSI TS 101 761-1 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part 1: Basic Data Transport Functions or ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part 2: Radio Link Control (RLC) sublayer), IEEE 802.15.3, and Bluetooth communication. Regarding IEEE 802.11 specifications, there exists extended specifications of IEEE 802.11a (for example, refer to Supplement to IEEE Standard for Information Technology-Telecommunications and Information Exchange between systems-Local and Metropolitan Area Networks-Specific Requirements-Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High-speed Physical Layer in the 5 GHZ Band), IEEE 802.11b, and IEEE 802.11g due to a wireless communication system and differences in frequency bands.
In the wireless network, the communication range of each terminal is limited to a distance where radio waves reach. For this reason, a communication party is not typically within the communication range of the local station, presenting the problem in that the usage efficiency of the network is decreased. Therefore, it is considered that “multi-hop transmission” by which a large number of terminals are connected to one another without the intervention of access points is promising. According to multi-hop transmission, it is considered that the frequency usage efficiency can be increased.
When communication is performed among terminals on the basis of a multi-hop technique, for example, the terminal of the transmission source broadcasts packets in the communication range of the terminal itself. Hereinafter, another terminal that is able to receive the packets repeatedly performs the operation of further re-broadcasting the received packets in the communication range of the terminal itself until all the terminals receive the packets (for example, refer to U.S. Pat. No. 5,740,363).
A proposal has been made on traffic routing in a small-sized wireless data network (for example, refer to PCT Japanese Translation Patent Publication No. 2002-512479). In this case, in a node of the wireless network, when receiving data in which a route identifier and a route updating message are attached are relayed, a route table is updated on the basis of a route updating message attached to the received message data, a neighbor node from the route table is selected, the route identifier and the route updating message are replaced on the basis of the updated route table, and message data in which the replaced route identifier and the replaced updating message are attached is transferred to the neighbor node.
According to the multi-hop technique, the communication station of the transmission source performs communication via a peripheral station that exists in the neighborhood. As a result, when compared to the case in which communication is directly performed with a receiving station at a far distance, the transmission power is reduced, and communication with a communication station or an access point at a far distance becomes possible.
In order to construct a local area network by using wireless technology, in general, a method is used in which one apparatus serving as a control station called an “access point” or a “coordinator” is provided in the area, and a network is formed under the centralized control of this control station.
In the wireless network in which access points are arranged, when information is transmitted from a particular communication device, an access control method based on band reservation is widely adopted in which, first, a band necessary for the information transmission is reserved at the access point so as to use the transmission path so that a collision with information transmission from another communication device does not occur. That is, epoch-making wireless communication is performed such that, as a result of arranging access points, communication devices within the wireless network are synchronized with one another.